Police say inquiries into an attack in Bradford which left a man seriously injured are being hampered because no witnesses have come forward.
On Sunday evening, about seven young men set upon the 20-year-old in the middle of the road in Legrams Lane.
The man was further attacked behind some houses and is likely to be off work for some months.
Det Ch Insp Ingrid Cannon said some people must have seen what happened but no one has given any information.
She explained that in the attack in the road one of the gang was wielding a hammer and traffic came to a stop.
In the attack behind the houses a plank of wood was used and some people looked out of their windows.
"We estimate the whole incident lasted about 15 minutes," Ms Cannon added.
"Even though we know some people must have seen what was happening, we have not had any witnesses coming forward nor did anyone ring 999.
"How would you feel if it was your son or brother or husband lying battered and bruised in a hospital bed?"
The suspects are described as Asian men, aged between 16 and 27.